1. Field of the Invention
The present invention relates to a method of packaging an electronic component applicable in an industry for assembling or mounting electric components.
2. Description of the Related Art
In industrial sectors in which electronic components such as a chip component and an IC component are mounted on a printed circuit board, external heat action or the like often causes a longitudinal or transverse expansion and contraction of the printed circuit board during or before mounting an electronic component onto the printed circuit board, partly because the use of materials having a high thermal conductivity has become common.
The mounting position of an electronic component onto the printed circuit board is previously programmed into a controller so as to permit sequential processing in accordance with such a positional value.
When mounting the electronic component in accordance with this program, therefore, there occurs a shift of the mounting position by an amount of change in expansion or contraction, thus resulting in an inaccurate mounting position and hence in occurrence of defectives.
It is therefore necessary, prior to mounting, to correct data in the foregoing program in compliance with the expansion/contraction ratio of the printed circuit board, and for this purpose, there is known a method disclosed in Japanese Examined Patent Publication No. 7-38519.
In this method, as shown in FIG. 9, when the lengths L1 and L2 between the recognition marks a and b and between b and c placed on the printed circuit board 50 show changes in the X-axis and the Y-axis directions by heat or the like into lengths L1' and L2' between the recognition marks a' and b' and between b' and c', it has been the conventional practice to calculate changes on the X-axis and Y-axis, respectively, from contraction ratios at X-axis=L1'/L1 and Y-axis=L2'/L2, and correct the coordinates of the mounting position as a whole on the printed circuit board 50 on the basis of the values thereof.
However, these changes in expansion and contraction of the printed circuit board are not uniform throughout the entire board, but are often non-uniform between different portions thereof. A proportional correction with multiplication and division of the contraction ratio cannot give a sufficient positional accuracy of mounting, and a larger value of coordinates leads to a proportional increase in error of the correction of multiplication/division of the foregoing contraction ratio, thus further reducing the mounting coordinates.
The conventional art had these various problems as described above.